TY  - BOOK
AU  - Gardner,Martin
TI  - Penrose tiles to trapdoor ciphers
U1  - 793.74 G226P 1988 
PY  - 1988///
CY  - New York
PB  - W. H. Freeman and company
KW  - Mathematical recreations
KW  - Triangle
KW  - Juvenile literature
N1  - Index
ER  -